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HomeAircraftHelicopterHelicopter Main Discussion › Tail boom mount differences
07-10-2018 02:43 PM  4 months agoPost 1
RM3

rrElite Veteran

Killeen, Texas - USA

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hello all.
So I have a question that needs an experienced opinion...
Lately I have been playing around with the idea of extending the tail boom on a Radikal to allow the model to comfortably swing 800mm blades (a LHS G800 gasser project), other mods will make this a reality like gearing, larger main shaft, engine, weight distribution.... but Radikals have a rather short Tail boom mount relative to say even a Trex 600. On Aligns helis, the tail boom mount is nearly twice as long, uses 6 screws per side to mount to the frame VS as the Radikals which uses just 4 per side and is short in comparison.
Being an amateur "engineer" I think this is a rather weak mount that allows too much stress in a small area compared to the Aligns setup which distributes the load over a bigger mounting area of the frame sides.
I like some (large) models that have longer boom mounts, those that extend to the main shaft bearings have significant advantages. I dont want to rely solely on tail boom support rods above and below (like Ive seen on one model).

So are tail boom mounts that critical in terms of vibration tolerance, rigidity and overall frame support integrity? Or are support structures like boom support rods enough to mitigate those flaws?

showing a preference will only get you into trouble, 90% of everything is crap...

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07-10-2018 05:47 PM  4 months agoPost 2
Heli Fanatix

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Fountain Valley, CA

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From my personal experience with many brands, customization and stretching booms. I noticed the walls of the boom is more critical.

Had CF that vibrates like crazy b/c of their wall thickness.

Never had a issue [once the wall is thick enough] throughout the many brands.

Some use double clamp type [logo xxtremes]. It’s not like the boom block like Align. Stretch from 700 to 800 with no issues.

We’ve learn that hand tighten and pinning the boom is sufficient. Over tighten enducese vibrations. Longer boom will give better tail authority b/c of the increase mechanical leverage.

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07-10-2018 06:12 PM  4 months agoPost 3
ICUR1-2

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Ottawa, Ontario

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When you consider how far into the boom support the tail goes....
almost all only go in a couple of inches anyways ..

I think the tail boom supports is more critical on stretched conversions

spending time, paying attention

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07-10-2018 08:17 PM  4 months agoPost 4
RM3

rrElite Veteran

Killeen, Texas - USA

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My concern is more on how the block length supports the frame. I know that the boom itself only needs to go into the block no more than 2 inches to grip it securely (be it pinned or clamped pref both) and that the boom wall thickness has alot to do with rigidity and vibs. Im just not sure if going with a longer boom "block" in which it mounts into then attaches to more area of the frame is worth the time in machining one, one that may incorporate the main shaft bearings as well OR if going with a short one and relying on the frame sides and supports to do all the work is enough.

showing a preference will only get you into trouble, 90% of everything is crap...

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07-10-2018 09:52 PM  4 months agoPost 5
ICUR1-2

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Ottawa, Ontario

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I guess at this point with out seeing the design. I would suggest making it bigger if you're able.
You Will need to decide if the time is worth it.

spending time, paying attention

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07-10-2018 11:38 PM  4 months agoPost 6
Dan Minick

rrKey Veteran

Columbus, WI

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Is there any way you could simply make a tube doubler that slips inside your existing 800 tube for the first 6-8 inches or so?

Team Synergy, Team FBL Rotors-------if its not broke...it will be!

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07-10-2018 11:56 PM  4 months agoPost 7
Heli Fanatix

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Fountain Valley, CA

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It’s not worth the time customizing the boom block.

Base on what you were trying to do, it will be similar to a goblin 500~770 main frame.

If it sets our mind at ease, look at the
- Velos
- Most 800 models, not much different from their 700 models
- if we give it some consideration, the boom just ties the tail rotor system to the main pod section. It’s job is to point the pod in the right direction. How much strength would we need?

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07-11-2018 01:15 AM  4 months agoPost 8
RM3

rrElite Veteran

Killeen, Texas - USA

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good point. especially since the Goblin simply ties to the back end of the frame. but it is a tapered tail section rather than a straight tube... so it sorta combines the tube and support rods all into one. I like the Velos, its built like a tank and Im sure that was done for a reason. but your right, the trex800 uses roughly the same tail boom block dimensions as the 600 relatively speaking.

showing a preference will only get you into trouble, 90% of everything is crap...

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07-11-2018 01:33 AM  4 months agoPost 9
Flyin for Jesus

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Troy, IL. 62294

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As long as the block is deep enough so that the end of the boom does not mash in allowing the reat of the boom to wiggle, then that's all you need.

With a rigid enough boom. you could grab 1" and still be fine. Too thin where the walls will colapse some, then it will need to be deeper.

On the Goblin booms, they are held with 2 plastic screws inline and 2 small screws through the frame however the boom is vrey rigid so there are no issues.

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07-17-2018 04:08 PM  4 months agoPost 10
Richardmid1

rrProfessor

Leeds, England

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It's the rear boom clamp and supports that give it the rigidity. Just get some longer and more heave duty boom supports, maybe from a Trex 800? You need a solid metal boom clamp aswell.

60% of the time, it works every time!

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07-17-2018 04:26 PM  4 months agoPost 11
Flyin for Jesus

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Troy, IL. 62294

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Longer boom supports do not mean more rigidity. The longer they are, the less angle you have between the two supports. ( assuming the same mounting at the frame )

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07-17-2018 06:40 PM  4 months agoPost 12
RM3

rrElite Veteran

Killeen, Texas - USA

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What about the size of the boom block itself?... it seems the shorter it is the more stress it puts at the rear of the frame. The longer it is the more it can extend inward towards the main shaft bearings and thus the more of the side frames it supports.

showing a preference will only get you into trouble, 90% of everything is crap...

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07-18-2018 01:10 AM  3 months agoPost 13
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

I agreed with more strong boom... 4% of main rotor torque is on tail rotor boom...

The length of boom is similar to the length of belt.

The secret? Balance of the tail rotor...

/

Saludos cordiales,

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